procedure TForm1.BitBtn2Click(Sender: TObject);
const
  StartText = 'Current IP Address: ';
  EndText = '</body>';
var
  StartPos, Leng: integer;
  HTMLBody, IP: string;
  PostData: TStringList;
  Response: TStringStream;
begin
  Response := TStringStream.Create('');
  PostData := TStringList.Create;
  try
    HTTP.Post('http://checkip.dyndns.org/', PostData, Response);
    Memo1.Lines.Text := Response.DataString;      // данные которые вернулись :))
  finally
    Response.Free;
    PostData.Free;
  end;
  HTMLBody := Memo1.Text;
  StartPos := Pos(StartText, HTMLBody) + Length(StartText);
  Leng := Pos(EndText, HTMLBody) - StartPos;
  IP := Copy(HTMLBody, StartPos, Leng);
  Label1.Caption := IP;
end;

<?
  echo $REMOTE_ADDR;
?>